From time to time in the past, proposals have been made to provide engine pistons and other combustion wall defining surfaces of an engine with insulating means, such as ceramic coatings or inserts, air gaps and the like. Such proposals have had various purposes, including raising combustion temperatures, reducing heat losses, improving engine efficiency, reducing wall quenching and reducing exhaust hydrocarbons and other undesirable exhaust emissions. Generally, however, proposed insulated piston designs have not been found satisfactory for reasons such as difficulty or incapability of manufacture, inadequate durability or limited insulating capability insufficient to obtain the desired control of heat flow. Thus, little use has so far been made, to applicants' knowledge, of insulated piston and combustion chamber constructions in practical production engines.